aTmega8驱动CD4021,实际程序为74165程序，在P/S口加反相器。 在实际电路中应注意TTL与CMOS电平转换-aTmega8 drive CD4021, and the actual procedure for the 74165 program, plus the P/S port inverter. TTL and CMOS level conversion should be noted that in the actual circuit